Science Buddies: "Ask an Expert"

I am trying to help my niece. She loves music. I am trying to educate her to be an informed consumer. I imagine the headphones and speakers kids think cool I are worth far less than they cost. She and I agree the science fair would be a great opportunity to show the difference from the highest priced to the reasonably priced units without embarrassing any one or group.

THS, peak and RMS specifications and easy to find as well as driver size, material etc.. The kids together seemed focused on nothing but base. I have found the formulas for calculating volume of air movement but air that moves hair does not rattle your teeth (apparently a good thing). Is there a device I can purchase or build (with her) that measures the force (not volume, I understand they are related), of the 25 to 65Hz. I know I can record the low frequency but with my speakers the results are disappointing.

I apologize for my ignorance. My brother succumbed to cancer and my mom is not best suited to this project. Can I make a science project (maybe a clear mannequin with some gel inside, some of the gel colored to show the low frequency sounds penetrating and disturbing the colored gel? Crepe paper outside the mannequin would show air moving but not influencing the gel.

For an instrument that would give values to the air displaced that does not penetrate deeply- outside an anemometer is there a more precise tool?

The bigger problem - Is there a device that gives a numeric value to the thumping and shaking caused by low frequency sound, outside a seismogram. If possible I would like help her build the meter that illustrates the depth and shaking of internal organs. I doubt paper being moved by a speaker cone would do much for her grade.

Not being in the music industry I know nothing of such devices.

Hopefully links of how to build such a device, doing so and good presentation will earn her high marks.

Thank you very kindly.
David Stephens
=== moderator: In keeping with Science Buddies policy to not post personal contact information, I deleted your phone number. Thank you for following our guidelines.

Hi HYRDGUN,
This is a very interesting topic! Unfortunately, I am having a little trouble wrapping my head around the hypothesis based on air volume though. I did a quick google search with the key term "headphone measurement software" and came across this company called Listen, Inc. They have a couple of test setup for headphones and one of the measurement is for Maximum sound pressure level.

Here's the URL:
https://www.listeninc.com/applications/ ... /#tab-id-3

Hope this is of some help to get you and your niece started on this experiment.
Good Luck and please let us know if there's anything else we can do to help.
Willey

Having read THE URL...
AND understanding that the pressure felt by the body would contain a fair amount of distortion vs the desired notes that make up "music" the artist intended. What measure of "sound" / "pressure" / "vibration" would accurately describe the (seat of the pants) sensation that makes music feel all encompassing? i.e. more than just the aural tones that transport us mentally. What is the name of the pressure or energy that passes though our body and fills our body, not just head with the rhythmic "FEELING" of the music. I know a loud speaker does it. How is that energy measured and in what unit of measure??? Thank you very much! I would like to buy future speakers with this (unnamed specification) as a part of my decision making progress.

Hi HYDRGUN,
I think what the term you are looking for is sensitivity or more specifically voltage sensitivity of the speaker. (measured in Watts / meter) Here's another resource that does a pretty good job explaining this topic:
http://www.psbspeakers.com/articles/Gui ... ifications

Good Luck!
Willey

I greatly appreciate your time and information. Unfortunately I was hopeful there was a standard measure other than watts. Every speaker reports watts in peak and RMS. I was in search of a more objective measure to indicate the amount of bass the speaker creates Decibel indicates volume across all the frequency range. I had hoped to evaluate speaker purchases by bass whether audible or not.

Thank you.

Hi Hyrdgun,

Another term you are looking for is "frequency response" which shows a speaker's loudness at different frequencies, not averaged across the entire frequency range. We have an abbreviated project idea (meaning it just provides some initial background information, it does not give you full instructions for the project) that you might find useful, including the references on the Background tab:

https://www.sciencebuddies.org/science- ... p102.shtml

In short, you can search for a "tone generator" app or website that lets you play sound at a specific frequency. Play that sound through your speakers. Then, use a separate "decibel meter" app to measure the volume of sound at each frequency. If you do this test for different speakers, you can compare their frequency response.

Another option is to search for an "audio spectrum analyzer" or "audio spectrometer" app, which will automatically display the sound intensity at different frequencies for you. You could play white noise (https://en.wikipedia.org/wiki/White_noise) - which has equal intensity at different frequencies - and look at the frequency response for each speaker.

You might not see the frequency response information on the box or on the speakers themselves, but if you google the company and model number you might be able to find more information online. Then your niece could compare her own tests to the advertised information.

Your niece could also do some background reading about how humans perceive sound - we have different sensitivity to sound at different frequencies. This page is a good start:

https://en.wikipedia.org/wiki/Loudness

Hope that helps,

Ben

*edit - one additional answer to your earlier questions - the unit of measure we actually "feel" is pressure, which is measured in Pascals: https://en.wikipedia.org/wiki/Sound_pressure. Normally our ears pick up variations in pressure but as you mentioned you can feel very loud bass with the rest of your body. Since humans have such a huge volume range of hearing (e.g. from rustling leaves up to a chainsaw or a jet engine) we use decibels, a logarithmic scale, to measure volume - basically that lets us measure sound from 0-120ish dB instead of 0-1,000,000,000,000ish dB - it makes the numbers more manageable. This is described a little more in the link Willey posted.